/* return a bound for T_2(P), P | polbase in C[X]
* NB: Mignotte bound: A | S ==>
* |a_i| <= binom(d-1, i-1) || S ||_2 + binom(d-1, i) lc(S)
*
* Apply to sigma(S) for all embeddings sigma, then take the L_2 norm over
* sigma, then take the sup over i.
**/
static GEN
nf_Mignotte_bound(GEN nf, GEN polbase)
{
GEN G = gmael(nf,5,2), lS = leading_term(polbase); /* t_INT */
GEN p1, C, N2, matGS, binlS, bin;
long prec, i, j, d = degpol(polbase), n = degpol(nf[1]), r1 = nf_get_r1(nf);
binlS = bin = vecbinome(d-1);
if (!gcmp1(lS)) binlS = gmul(lS, bin);
N2 = cgetg(n+1, t_VEC);
prec = gprecision(G);
for (;;)
{
nffp_t F;
matGS = cgetg(d+2, t_MAT);
for (j=0; j<=d; j++) gel(matGS,j+1) = arch_for_T2(G, gel(polbase,j+2));
matGS = shallowtrans(matGS);
for (j=1; j <= r1; j++) /* N2[j] = || sigma_j(S) ||_2 */
{
gel(N2,j) = gsqrt( QuickNormL2(gel(matGS,j), DEFAULTPREC), DEFAULTPREC );
if (lg(N2[j]) < DEFAULTPREC) goto PRECPB;
}
for ( ; j <= n; j+=2)
{
GEN q1 = QuickNormL2(gel(matGS,j ), DEFAULTPREC);
GEN q2 = QuickNormL2(gel(matGS,j+1), DEFAULTPREC);
p1 = gmul2n(mpadd(q1, q2), -1);
gel(N2,j) = gel(N2,j+1) = gsqrt( p1, DEFAULTPREC );
if (lg(N2[j]) < DEFAULTPREC) goto PRECPB;
}
if (j > n) break; /* done */
PRECPB:
prec = (prec<<1)-2;
remake_GM(nf, &F, prec); G = F.G;
if (DEBUGLEVEL>1) pari_warn(warnprec, "nf_factor_bound", prec);
}
/* Take sup over 0 <= i <= d of
* sum_sigma | binom(d-1, i-1) ||sigma(S)||_2 + binom(d-1,i) lc(S) |^2 */
/* i = 0: n lc(S)^2 */
C = mulsi(n, sqri(lS));
/* i = d: sum_sigma ||sigma(S)||_2^2 */
p1 = gnorml2(N2); if (gcmp(C, p1) < 0) C = p1;
for (i = 1; i < d; i++)
{
GEN s = gen_0;
for (j = 1; j <= n; j++)
{
p1 = mpadd( mpmul(gel(bin,i), gel(N2,j)), gel(binlS,i+1) );
s = mpadd(s, gsqr(p1));
}
if (gcmp(C, s) < 0) C = s;
}
return C;
}
int do_factor(GEN n, long prec)
{
pari_sp ltop;
GEN sq = gfloor(gsqrt(n, prec));
GEN q = stoi(2);
ltop = avma;
for (;;) {
if (cmpii(q, sq) > 0)
return -1;
if (equalsi(0, gmod(n, q))) {
pari_printf("%Ps = %Ps * %Ps\n", n, q, gdiv(n, q));
return 0;
}
gaddz(gen_1, q, q);
avma = ltop;
}
}
/* d = requested degree for subfield. Return DATA, valid for given pol, S and d
* If DATA != NULL, translate pol [ --> pol(X+1) ] and update DATA
* 1: polynomial pol
* 2: p^e (for Hensel lifts) such that p^e > max(M),
* 3: Hensel lift to precision p^e of DATA[4]
* 4: roots of pol in F_(p^S->lcm),
* 5: number of polynomial changes (translations)
* 6: Bezout coefficients associated to the S->ff[i]
* 7: Hadamard bound for coefficients of h(x) such that g o h = 0 mod pol.
* 8: bound M for polynomials defining subfields x PD->den
* 9: *[i] = interpolation polynomial for S->ff[i] [= 1 on the first root
S->firstroot[i], 0 on the others] */
static void
compute_data(blockdata *B)
{
GEN ffL, roo, pe, p1, p2, fk, fhk, MM, maxroot, pol;
primedata *S = B->S;
GEN p = S->p, T = S->T, ff = S->ff, DATA = B->DATA;
long i, j, l, e, N, lff = lg(ff);
if (DEBUGLEVEL>1) fprintferr("Entering compute_data()\n\n");
pol = B->PD->pol; N = degpol(pol);
roo = B->PD->roo;
if (DATA) /* update (translate) an existing DATA */
{
GEN Xm1 = gsub(pol_x[varn(pol)], gen_1);
GEN TR = addis(gel(DATA,5), 1);
GEN mTR = negi(TR), interp, bezoutC;
gel(DATA,5) = TR;
pol = translate_pol(gel(DATA,1), gen_m1);
l = lg(roo); p1 = cgetg(l, t_VEC);
for (i=1; i<l; i++) gel(p1,i) = gadd(TR, gel(roo,i));
roo = p1;
fk = gel(DATA,4); l = lg(fk);
for (i=1; i<l; i++) gel(fk,i) = gsub(Xm1, gel(fk,i));
bezoutC = gel(DATA,6); l = lg(bezoutC);
interp = gel(DATA,9);
for (i=1; i<l; i++)
{
if (degpol(interp[i]) > 0) /* do not turn pol_1[0] into gen_1 */
{
p1 = translate_pol(gel(interp,i), gen_m1);
gel(interp,i) = FpXX_red(p1, p);
}
if (degpol(bezoutC[i]) > 0)
{
p1 = translate_pol(gel(bezoutC,i), gen_m1);
gel(bezoutC,i) = FpXX_red(p1, p);
}
}
ff = cgetg(lff, t_VEC); /* copy, don't overwrite! */
for (i=1; i<lff; i++)
gel(ff,i) = FpX_red(translate_pol((GEN)S->ff[i], mTR), p);
}
else
{
DATA = cgetg(10,t_VEC);
fk = S->fk;
gel(DATA,5) = gen_0;
gel(DATA,6) = shallowcopy(S->bezoutC);
gel(DATA,9) = shallowcopy(S->interp);
}
gel(DATA,1) = pol;
MM = gmul2n(bound_for_coeff(B->d, roo, &maxroot), 1);
gel(DATA,8) = MM;
e = logint(shifti(vecmax(MM),20), p, &pe); /* overlift 2^20 [for d-1 test] */
gel(DATA,2) = pe;
gel(DATA,4) = roots_from_deg1(fk);
/* compute fhk = hensel_lift_fact(pol,fk,T,p,pe,e) in 2 steps
* 1) lift in Zp to precision p^e */
ffL = hensel_lift_fact(pol, ff, NULL, p, pe, e);
fhk = NULL;
for (l=i=1; i<lff; i++)
{ /* 2) lift factorization of ff[i] in Qp[X] / T */
GEN F, L = gel(ffL,i);
long di = degpol(L);
F = cgetg(di+1, t_VEC);
for (j=1; j<=di; j++) F[j] = fk[l++];
L = hensel_lift_fact(L, F, T, p, pe, e);
fhk = fhk? shallowconcat(fhk, L): L;
}
gel(DATA,3) = roots_from_deg1(fhk);
p1 = mulsr(N, gsqrt(gpowgs(utoipos(N-1),N-1),DEFAULTPREC));
p2 = gpowgs(maxroot, B->size + N*(N-1)/2);
p1 = gdiv(gmul(p1,p2), gsqrt(B->PD->dis,DEFAULTPREC));
gel(DATA,7) = mulii(shifti(ceil_safe(p1), 1), B->PD->den);
if (DEBUGLEVEL>1) {
fprintferr("f = %Z\n",DATA[1]);
fprintferr("p = %Z, lift to p^%ld\n", p, e);
fprintferr("2 * Hadamard bound * ind = %Z\n",DATA[7]);
fprintferr("2 * M = %Z\n",DATA[8]);
}
if (B->DATA) {
DATA = gclone(DATA);
if (isclone(B->DATA)) gunclone(B->DATA);
}
B->DATA = DATA;
}
